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MAY 2009
Email: [email protected]: www.concpipe.asn.au
News and Information from the Concrete Pipe Association of Australasia
Concrete Pipe Association of
Australasia
The standard for reinforced concrete pipe, AS/NZS4058 “Precast Concrete Pipe (Pressure and Non-Pressure)” defines the materials, manufacturing requirements, product characteristics, and performance durability criteria required for reinforced concrete pipe. It outlines that product made to this standard, and installed in accordance to AS/NZS3725 “Design for the Installation of Buried Concrete Pipes” can achieve a service life of 100 years.
Traditionally concrete pipe manufacturing in Australia and New Zealand has been based on spun and rolled techniques which uses substantial centrifugal or roller forces to compact the material. As a result concrete with a low water/cement ratio can be used, resulting in a material of high strength and low permeability. This allows for a thin walled concrete pipe to be made and results in depths of cover to reinforcement not as great as may readily be adopted for in-situ structures, or many other types of precast concrete product. This is reflected in Table 3.1 of AS/NZS4058 which nominates a cover depth of 10mm minimum for barrels of machine-made pipe having wall thickness greater than 35mm in a normal environment. The cover depths outlined in the standard can be justified by the service history of Australian and New Zealand made pipe over 90 years and the high quality of concrete used in manufacturing concrete pipes. This forms the basis of the 100 year service life outlined in the standard, and the durability is reflected by the specified low values of water absorption. By contrast other parts of the concrete industry use compressive strength as the benchmark of quality, and a series of other tests have been developed to assess properties related to durability.
To demonstrate the differences between pipe concrete and insitu concrete, GHD, one of Australia’s leading multi-disciplinary engineering companies, was commissioned by the CPAA to utilise their experienced independent testing expertise. GHD was asked to conduct a test program to demonstrate that (a) water absorption in
accordance to AS/NZS4058 is a viable measurement for durability when compared to other concrete durability tests, and (b) that the concrete used in pipe is a more durable material than typical 50 MPa insitu concrete.
A number of samples taken from concrete pipes (DN600 and DN675), 50 MPa concrete cylinders and cores from 50 MPa cast insitu concrete were collected. These samples were all cured under controlled and typical conditions for concrete pipe and insitu concrete, and tested for water absorption (in accordance to AS/NZS4058) and for sorptivity (in accordance to the world wide recognised GHD method). The test results indicated that precast concrete pipe made in accordance to AS/NZS4058 exhibits lower water absorption compared to cast insitu concrete and concrete cylinders as well lower sorptivity. Added to this the concrete pipe results were all lower than the industry benchmarks - <6% for water absorption and <0.09mm/min0.5 for sorptivity.
The report goes on to conclude that the current test results for absorption and sorptivity in addition to the documented industry experience suggest that precast pipe concrete is likely to exhibit higher durability in comparison to cast in situ concrete of a similar mix design and cover, provided that the following parameters, outlined in AS/NZS4058, are achieved in production:
Maximum water to cement ratio 0.35-0.40•Minimum binder content of 330 kg/m• 3
Water absorption less 6%•
The report also concludes that the minimum cover requirements of AS/NZS 4058 have been developed on this premise.
HoW DurAbLe is ConCreTe PiPe ?
MAY 2009
The GHD report concluded that;
“.. the low water cement ratio mixes used in precast concrete pipe, combined with the high level of compaction achieved by the spun and rolled manufacturing processes and controlled curing gives increased resistance to aggressive agents in comparison to cast insitu or regular
precast concrete concrete.”
MAY 2009
The water absorption test
Even allowing for the high quality of concrete that is used in pipes, the cement is mixed with more water than will eventually combine to build the structure of the hardened cement paste. Strong and durable concrete is characterised by minimal void space created by the excess water – hence water absorption provides an index of the quality of concrete, related to both these properties. Water absorption of cores taken from concrete pipe products represents the concrete actually in the product, unlike test cylinders which are a measure of the quality which the concrete can achieve given appropriate treatment.
The water absorption test outlined in Appendix F of AS/NZS4058 “Precast Concrete Pipes” provides an indicator of the quality of the concrete used for the pipe. It has been the industry standard classification and control test for the durability of reinforced concrete pipe for over 40 years. The test measures the increase in weight of an oven dried test specimen, which is caused by the absorption of water under controlled and specified conditions. It is expressed as a percentage of the initial oven dry weight of the specimen, and in accordance with AS/NZS4058, the water absorption shall not exceed 6%.
To demonstrate the CPAA’s value on this test, a number of sample cores taken from concrete pipe manufactured by CPAA member companies have been independently examined for water absorption. The samples, taken over the last two years, have resulted in mean water absorption of 4.5% (with a standard deviation of 0.8), well below the industry benchmark of 6%.
other tests
AS/NZS4058 outlines a number of other performance tests that must be carried out by manufacturers to demonstrate compliance of finished concrete pipe.
These other tests that are also included in the Standard are:
•Testproofloadtesting
•Ultimateloadtesting
•Watertightness(formerlyknowashydrostatictesting)
•Specifiedandultimatepressuretests
•Flexiblejointassembly
•Measurementofconcretecovertoreinforcement
•Measurementofdimensionsotherthanconcretecover
Added to this, CPAA members have strict quality control procedures for the manufacture of concrete pipe, that are implemented to ensure the whole manufacturing process is accounted for. In particular this includes the mixing and batching of concrete, with appropriate aggregates, admixtures and binders, using:
•Computercontrolledweighingandproportioningsystems.
•Computercontrolledmixingsystems.
•Automatedrecordingsystems.
The quality systems are also required to ensure that the welding of steel reinforcement into cages is carefully monitored and tested to ensure compliance.
TesTing ProCeDures for ConCreTe PiPe
Concrete pipe tested for watertightness
A core sample being tested for water absorption
Concrete pipe subjected to proof load testing
MAY 2009
ConCreTe reDuCes PiPeLine’s environMenTAL fooTPrinT
Client: NewGen Kwinana Power StationProject Manager: ERM Power Pty LtdContractor: Smithbridge AustraliaProduct: 1800DN outfall marine grade skid ring pipes
A new marine outfall pipeline has been built in Western Australia with minimal impact on the local aquatic environment due in part to the use of precast concrete pipes.
A number of precast concrete pipes, along with other concrete elements, were recently used to construct the cooling water outfall pipeline at NewGen Kwinana Power Station because they aided construction techniques designed to reduce the project’s environmental footprint. ERM Power Pty Ltd, a partner in the NewGen Kwinana Project, is responsible for the overall procurement and project management of the power plant. The 1800mm diameter pipeline extends 320m into the Indian Ocean at Cockburn Sound where it discharges cooling water through an integral seabed diffuser array. Marine construction specialist Smithbridge Australia chose to build the outfall pipeline from a 10m wide temporary bridge that was built with precast concrete deck planks to act as the working platform along the full length of the concrete pipeline. This construction method was chosen because the area of disturbance to the existing seabed was significantly reduced from what it would have been had the pipeline been laid in an open trench requiring rock armour protection on the resulting side batters. And, unlike traditional open trench excavation from a moored barge, the temporary bridge also offered better access, the ability to work in adverse weather and a safe work platform for crane operations. The pipeline was then laid by divers within a sheet pile cofferdam that was progressively moved along the bridge positioned on the outfall alignment The precast outfall concrete pipes were manufactured by a CPAA member to suit the project.
Useofasheetpilecofferdam furtherminimised the footprinton the existing seabed and sediment plumes produced by the excavation, pipe laying and backfilling operations were able to be contained. This was of particular importance to the neighbouring Perth Seawater Desalination Project, whose seawater intake structure was only 60m from the pipeline alignment. The challenging project was successfully completed with close involvement of the concrete pipe manufacturer according to Smithbridge Australia. The decision to use concrete was made because they were the most cost-effective yet durable of the four pipe products considered.
The contractor was extremely happy with the way the CPAA member helped out with their efficient, organised manner and the quality of the custom designed precast concrete pipes. This involved the production and supply of Class 2 and Class 4 pipes with a skid ring type suitable for underwater jointing and extra cover reinforcement for marine conditions (in accordance to AS/NZS4058). Twenty-one of the pipes were produced with a blockout and a factory-fitted concrete pipe diffuser offtake was also incorporated. Three purpose-made factory splays were also fabricated to make it possible for the pipeline to change direction.
Concrete pipe being installed under the cofferdam
The concrete pipes waiting to be installed
New Zealand
MAY 2009
Concrete Pipeline Design WorkshopsThe CPAA is pleased to be associated with the “Reinforced Concrete Pipes and Pipeline Design Workshops” to be conducted in 2009 by Cement Concrete Services. The workshop will look at the comprehensive design of concrete pipeline systems in accordance to the appropriate standards AS/NZS4058 and AS/NZS3725. Details for the first three courses are:
NSW – Monday 16 March 2009 Stamford Grand Hotel, North Ryde
QLD – Thursday 14 May 2009 Mercure Hotel, Brisbane
VIC – Thursday 18 June 2009 Hotel Grand Chancellor, Melbourne
WA – (Date TBA), Hotel Ibis, Perth
NSW – Monday 12 October 2009 Stamford Grand Hotel, North Ryde
For more details visit the CPAA website www.concpipe.asn.au, the CCS website www.cementandconcrete.com or contact David Millar at [email protected]
Training - Laying Concrete PipesIPWEA (NSW) present the Concrete Pipe Laying Training Program for the CPAA at venues throughout NSW. The program is delivered by registered trainers in the construction industry in conjunction with the CPAA.
Dates and venues for 2009 are:
14th April, Dubbo10th June, Orange12th August, Sydney10th November, Queanbeyan
For details of a training program near you, or to organise a specific course in your area, contact Roisin Mullan at IPWEA on [email protected].
PipeClass workshopsThe Concrete Pipe Association of Australasia is running the PipeClass workshop in regional centres in Australia and New Zealand during 2009.
PipeClass is the reinforced concrete pipeline design program that the Concrete Pipe Association of Australasia (CPAA) offer to the industry, free of charge. The software allows the specifier to design concrete pipelines in accordance with the latest versions of AS/NZS4058 “precast concrete pipes” and AS/NZS3725 “Design for installation of buried concrete pipe” with confidence.
Workshops have already been held in Albury and Auckland this year, and are currently booked in Wollongong (11th June), Geelonmg (17th June), Traralgon (19th June), Newcastle (4th August), Port Macquarie (5th August), Echuca (24th August) and Mildura (25th Augus). Further workshops will be added to the schedule as the year progresses.
The workshop, presented by David Millar, Executive Director of the CPAA, will provide PipeClass users a detailed look at how to use the program, how to gain the maximum benefit in efficiency from the program, and an insight into some hidden extras that will provide value to your design. Go to the CPAA web site, www.concpipe.asn.au to register today.
CPAA Member Companies
Concrete Pipe Associationof Australasia [email protected] www.cpaa.asn.au
Australia
